In the field of an organic thin film transistor device, an organic thin film solar cell, an organic EL display and the like, many functional thin films are investigated. The functional thin film is a thin film subjected to so-called fine patterning, which includes a material exhibiting various functions and is arranged at locations where the functions needs to be exhibited in a device with precision required for exhibiting the functions. Examples of the functions to be exhibited by patterning include functions of wiring, an electrode, an insulating layer, a light-emitting layer, a charge transporting layer and the like. As a technique of performing such patterning, an ink-jet method, a nozzle coating method, and various roll printing methods, for example, a method of directly patterning a substrate by using flexo printing or reversing, are proposed. These printing methods use an ink which is usually relatively low in concentration and viscosity.
In the case where an ink of a high-molecular weight organic material is applied to produce an organic EL display, there is known a method of disposing a so-called bank serving as a separating wall for separation of pixels. This is a method in which functional thin films such as a charge injection layer, an intermediate layer (interlayer), a light-emitting layer and the like are applied to the inside of the bank by an ink-jet method or some other coating method, and dried to apply the functional thin films separately, and for example, a method of forming a bank using an inorganic insulating film (SiO2) and an organic insulating film formed thereon is proposed (Patent Document 1). However, in this method, there is a problem that the applied ink rises and spreads along the bank, and therefore a film having a sufficient thickness cannot be obtained. As a method for solving this problem, there is proposed a method in which a surface of the bank is subjected to processing for imparting liquid-repellency to suppress rising of the ink along the bank (Patent Document 2). This is a method in which a fluorine-based (CF4) plasma treatment is performed to enhance surface tension of the bank and improve ink retention force to obtain a desired thickness of the functional thin film.
As a specific example of a method in which a lyophilic region and a liquid-repellent region are formed by performing processing for imparting liquid-repellency on a surface of a substrate such a bank surface, there is known a method in which a liquid-repellent substance such as a fluorine-containing silane coupling agent is applied onto a surface of a lyophilic thin film to form a liquid-repellent thin film, a part of the liquid-repellent thin film is irradiated with light having a wavelength less than 200 nm to decompose the liquid-repellent substance, and then the decomposed product is removed. In the substrate obtained by this method, only a site irradiated with light becomes a lyophilic surface (Patent Document 3).
Further, as a method of using light with a relatively long wavelength, there is a method in which a thin film of a liquid-repellent composition, containing a compound having a liquid-repellent group and a photopolymerization initiator, is formed on a lyophilic substrate, and a part of the thin film is irradiated with light to polymerize the liquid-repellent composition and make the composition insoluble in a solvent, and an unpolymerized portion of the composition is removed by use of a solvent to pattern a lyophilic region (Patent Document 4).
Moreover, as a method of using ultraviolet light with a relatively long wavelength, there is also known a method in which a liquid-repellent thin film containing a photocatalyst such as titanium oxide is formed on a lyophilic layer and a part of the thin film is irradiated with light to decompose the liquid-repellent thin film and to pattern a lyophilic region (Patent Document 5).